/Engine/Source/Runtime/Datasmith/CADKernel/Public/CADKernel/Mesh/Structure/ThinZone2D.h
this will eventually be reconciled with what the Geometry team is using.
namespace UE { namespace CADKernel { enum EThinZone2DType { Undefined = 0, Global, PeakStart, PeakEnd, Butterfly, BetweenLoops, TooSmall, } } }